A radio frequency identification (RFID) system identifies unique items using an interrogator and an RFID tag. Typically, the interrogator communicates with the RFID tag that is attached to an item. The interrogator, also known as a reader, communicates with the RFID tag through radio waves and passes the information read from the RFID tag in digital form to a computer system. The RFID tag is typically a microchip that stores the digital information. The microchip is attached to an antenna that receives signals from and sends signals to the interrogator. The RFID tag includes a unique serial number and may include other information, such as a customer account number.
RFID tags can be active tags, passive tags or semi-passive tags. Active tags include a power source that powers the microchip's circuitry and transmits a signal to the interrogator. Passive tags do not include a power source. Passive tags draw the power required for the circuitry and the transmission of information from the electromagnetic field generated by the interrogator. Semi-passive tags are similar to active tags; however, the power source is used to run the microchip's circuitry but not to communicate with the interrogator. Some semi-passive tags are inactive until they are activated by a signal from the interrogator, which conserves life of its power source.